Hoofed Animals — Ungulates 3 
ORDER UNGULATA 
In this order are comprised all those animals which may 
be roughly described as hoofed animals, such as pigs, deer, 
sheep, oxen, horses, and elephants. Although some of these 
differ very markedly from one another, not only in outward 
appearance but also in internal structure, the study of the 
large number of allied fossil forms tends to bring them 
together. At the same time it is difficult to construct a 
diagnosis which will include them all. 
The following, however, brings out their most important 
characteristics: Ungulates are terrestrial and mainly vege- 
table-feeding mammals, with limbs adapted to progression 
and not to prehension, with from five to only one digit, the 
terminal phalanges of which are usually enclosed in a solid 
horny hoof, though in some cases there are broad, blunt 
nails; clavicles absent; humerus with no entepicondylar 
foramen; scaphoid and lunar bones always distinct; a full 
set of milk teeth not completely replaced until adolescence; 
molars broad with ridged or tuberculated crowns. 
This order, containing the largest of all living terrestrial 
animals, is not well represented in the fauna of the State of 
Colorado. Out of twelve recent families generally recog- 
nized only three are represented and these are all included 
in the suborder Artiodactyla, characterized by the predomi- 
nance of the third and fourth digits of the fore and hind 
limbs, which with their hoofs form a symmetrical pair, while 
the second and fifth are smaller and of no practical im- 
portance, or are wanting altogether. 
The following key shows the most conspicuous characters 
by which the families and genera may be distinguished. 
A. Frontal appendages in the form of true horns, i. e., a bony- 
process of the skull ensheathed by a hollow horny 
covering. 
